Rotary type selector switch for automatic telephone systems



Feb. 18, 1947. LONG 2,416,109

- ROTARY TYPE SELECTOR swITcH FOR AUTOMATIC TELEPHONE SYSTE'MS.

Filed Jan. 10, 1946' a &

INTERM/TTENT 84 771R) I E AITH D H" v DOUGLAS PERCY LONG Patented Feb.18, 1947 2,416,1091] I k ROTARY TYPE SELECTOR SWITCH FOR AUTOMATICTELEPHONE SYSTEMS Douglas Percy Long, Chislehurst, England, assignor toSiemens Brothers & Co. Limited, London, England, a British companyApplication January 10, 194.6, Serial No. 640,260

.In Great Britain January 1, 1945 This invention relates to automatictelephone systems and more particularly to the control of selectingswitches required to search in a group of outlets in accordance with amarkingap to their contact banks consequent on the receipt of a train ofimpulses. It has in view improved means for the control of a singlemotion selecting 9 Claims. (Cl. 179-18) switch by apparatus individualto the switch and using the minimum of control apparatus.

In a single motion selecting switch having a large number of outletswiper switching may be employed whereby the switch is constrained tosearch in one or other of two sets of banks. As the time available forsearching is limited by what is known as the inter-train pause thenumber of consecutive bank contacts which can be tested within thatperiod of time is dependent on the speed of operation of the switch.Owing to this limitation and the necessity for avoiding complicated oruneconomical wiper switching arrangements, arrangements have beenproposed in. which an increase in the number of outlets may be had byadapting the wipers to sweep two banks in succession, hereinafter termeda pair, and for search in the second of the .two banks a preliminarysetting is given to the wipers at thetime the selecting switch is takeninto use.

This may be efiected dependent on the path of entry to the selectingswitch or other discriminating action such as a signal,v from apreceding switching stage. The selecting switch may be taken into use inresponse to either of a pair of digital values received at a precedingswitching stage, the discriminating action serving to dis tinguishbetween the two digital values of'the pair. Outlets corresponding to onesuch value would then be accommodated in one of the two banks of thepair and outlets corresponding to the other of such digital values wouldbe accommodated in the other of the said two banks. In addition,afurther discriminating action may be had by wiper switching inaccordance with the digital value actually received at the selectingswitch.

In the present invention it is arranged that the stopping circuit forthe selecting switch is deimpulses may be received in the switch circuitand in accordance with the usual practice the dialling relay is operatedprior to receipt of the switch setting train. In its operated conditionthe diallingrelay connects the test relay in a circuit in which theoperation of the latter depends on a wiperreaching the contact in theselecting switch bank at the desired preliminary position. The selectingswitch has therefore to move to its preliminary position before thediallingrelay releases at the end of the impulse train; This is ensuredwithout imposing limitations on the disposition of the outlet byemploying a high speed selecting switch and a dialling relay with arelease lag long enoughto extend over the preliminary setting periodeven if only a single impulse has been received. In the other conditionof the dialling relay the test relay should be connected to the testwipers in the normal manner.

The discriminating action is conveniently effected by a relay which isoperated or not at the I time the selecting switch is taken into use andpendent on the condition of the dialling relay 'which is usuallyprovided to determine the end of an impulse train. In one condition ofthis relay the selecting switch may move to take up a'preliminaryposition adjacent to aset of outlet groups in response to a.discriminationefiected at the' ror wiper switching purposes. 4 withmid-normal contacts on the selecting switch which, in one conditioninitiates the preliminary movement of the selecting switch. A suitablerelay for the purpose is the wiper switching relay leased prior to thetime at which itsoperation may be required for wiper switching purposes,the circuit for the continued driving of the selecting switchbeingmaintained by other means after the release of the wiper switchingrelay. The discriminatin'g action may be brought about by means of asignal f'roma preceding circuit. The signal may conveniently take theform of an absence of potential onone of the line wires at the time ofswitching through whereby the relay isallowed to operate in'a loopcircuit to initiat the preliminary movement of the selecting switch. Onthe other hand, if no signal is to be transmitted a suitable potentialis applied to the said line wire to prevent operation of the relay.

While the contacts in the selecting switch bank on which the switch isto stop in its preliminary movement may be marked directly the outletsto besearched will be marked in a circuit including a contact of amarking device and a back contact of the dialling relay. The markingdevice may take the form of a stepping switch responsive to 'digits'andsuitably connected contacts may serve for the operation of thewiperswitching relay In conjunction .5 switch is stepped in accordance withthe impulses received. Relay C is held in this circuit during impulsereception. When the digit switch is stepped from its normal position theoif-normal contacts are operated. Contact DONI opens the operatingcircuit for relay C over its upper winding and contact DONZ prepares aselfstepping circuit for the digit switch for homing it. At the end ofthe impulse train relay C releases and at contact closes a circuit formagnet MU and at contact 06 connects earth to the contacts of the groupin the marking bank of the selector corresponding to the receivedimpulses. Contact 03 connects the test relay T over contacts b3 and ws3to the test wiper P and contact 01 opens a further point in the circuitfor magnet DM over the lower winding of relay C. Magnet MU operates in acircuit from earth over contacts b5, DONI, 05, H, hi, the, magnetwinding to battery and the wipers of the selector are rotated in searchof a free outlet in the group marked in accordance with the receiveddigit. Contact ON! disconnects the battery from wire p while theselector is off-normal Y portion, and over wiper M4 for the Z portion.

As for the moment consideration is only being given to the operation forselection in the W and Y portions of the bank the marking will beapplied over wiper MI and if search is to be made in the Y portion relayWS will be operated in a circuit from earth over contact bl, MNI, wiperM3, the right-hand Winding of the relay to bat.- tery. When the selectorWipers are rotated on to contacts in the wanted outlet oup earth overcontacts 06 wiper MI and marking wipers GI or G2 as the case may be,contact ws l and rectifiier MRA will be extended to the right handwinding of relay T and when a free outlet in the group is encountered,denoted by the presence of battery potential on the test wire, relay Twill operate over the above traced circuit from earth and over itsleft-hand winding and contacts 03, b3, ws3 wiper P to the batterypotential on the test wire. Contact H at its back contacts opens theoperating circuit for magnet MU and removes a short circuit from relayH, and at its front contact short-circuits the right hand winding ofrelay T and earths the test wiper over the low resistance left-handwinding of relay T to engage the outlet. Relay H operates from earthover contacts 0N2, 04, b4 and the winding of magnet MU. The magnet willnot hold in series with relay H and the rotation of the switch wipers isstopped with the wipers on the contacts of the free outlet. Contact hiopens a further point in the operating circuit for magnet MU, contactsh2, h3, b4 and b5 switch through the speaking and test wires and contacth8 opens a further point in the circuit for magnet DM. The extension ofearth over wire 10 and contacts M and 72.5 short circuits relay T whichthereupon releases. At contact 712 relay A is released and by thefalling back of contact a! relay B releases. Relay H remains held toearth on the test Wire applied in the succeeding switch consequent onthe operation of the release relay therein. Contact 193 disconnects thecircuit for relay T, contact 134 opens to leave relay H dependent on theearth fed back over the test wire, contact b5 opens in the op eratingcircuit for relay C and contact b6 closes in the homing circuit for thedigit switch. If no discriminating signal is to be transmitted from theselector the contact in the bank of wiper M1 corresponding to theimpulses received will be connected over contact cl to the positivespeaking wire and at the time the succeeding selector is taken into usethe impulse receiving relay therein will operate over a preceding loopto earth over the positive wire, contact cl, wiper M1 and contact b2.The wiper switching relay in the succeeding switch will be shunted bythis connection and will not operate. If, however, a discriminatingsignal is to be transmitted there will be no connection to contact clfrom the bank of wiper M1 and relay WS in the succeeding switch will beincluded in the loop circuit over which the impulse relay operates. Therelease of relay B will disconnect the shunting earth, if it has beenapplied, by which time the succeeding selector will have moved oil,-normal with the consequence to be described later.

It will now be assumed that at the time the selector shown in thedrawing is taken into use a discriminating signal is received and relayWS is operated in the manner above described. The early closure ofcontact ws5 closes a circuit, over contacts 05, ii, and hi for magnet MUand the selector is set in motion. As soon as the selector wipers movefrom their normal position contacts ONI and 0N2 are operated and thelatter close a circuit for magnet MU that is independent of contacts ws5and 05. In the meantime relay A has operated and operated relay B and acircuit has been closed over the upper winding of relay C, but by thistime the selector has moved off normal and the circuit for magnet MUrendered independent of relay C. Contact b2 on closure short circuitsrelay WS to release it. When relay C operates relay T is connected overcontact 03 to battery over resistance YA and the selector will continuein operation, contact c6 being open, until the wipers have madeatraverse of the W and Y portions of the bank. When wipers GI and G2reach the first contacts in the X and Z portions of the marking bank acircuit for-relay T will be provided over an earth connection to thesecontacts and the selector will be brought to rest. The release lag ofrelay C is arranged to'cover the period required for this rotation ofthe selector wipers, even if only one impulse has been received in theselecting digit, so that at the time of operation of relay T contact 04will be open and relay H will not be operated. In this position of theselector wipers contacts MNI and MN2 are operated. After the end of theimpulse train relay C will release and by this time relay WS will havebeen released. Contact 03 will open the circuit for relay T, releasingit, and with contact 05 closed magnet MU will again operat and theselector wipers will be driven over the X and Z portions of the bank.When the contacts of the outlet group marked over wiper M2, since the Xand Z portions of the bank are concerned this time, are encountered-thecircuit for the test relay is connected up and the individualoutlets ofth group are tested over wiper P in the manner before described and whena free outlet is met relays T and H are opwipers. will be without usefulefiect.

I contacts, N2.

I priate to selection in the W and X portions of j the bank. Ifselection is to be made in the Y or Z portions the impulses received bythe digit switch will be such that wiper M3 or M4 as the case may bewill be connected to relay WS and on the coming to rest of the digitswitch at the end of the impulse train relay WS will be operated and bymeans of its contacts wet-ava l the 1 connection to the selector wiperswill be changed over from the W and X wipe-rs to the Y and Z The closureof contact 1035 at this time If, during the search for a free outletnone is encountered in the marked outlet group the selector wiperscontinue to advance until the last contacts in that portion of the bankin which the selector in that position, the circuit being completed overthe appropriate test wiper P and the shunted upper winding of relay C.Relay C 1 operates in series with the test relay after its delay periodduring-which relay H is operated.

At contacts c2 and he a source of busy tone I is connected over theright hand winding of relay A and by induction into the middle windingis transferred over the last contacts in the several portions of thebank and wipers to the callers line, the return path being over thenegative wiper and the left-hand winding of relay A. At

1 the same time intermittent battery and earth are applied over themiddle winding of relay A i to give a flashing signal in known manner.During the period when battery is connected to all the windings of relayA the relay is held over its right hand winding and contacts hfi and 02to earth in the tone circuit. Earth on'wire in over contacts h l, b4,ed, M, MNZ, and one of the wipers M5 and M6 operates an overflow meter.

When the caller clears at the end of a con- .versation or on receipt ofbusytone earth is disconnected from the test wire, either at the circuitfrom which the connection is held or by the re- 3 lease of relay A in aninterval during which earth is connected over its middle windingfollowed by release of relay B. Relay H releases and recloses thecircuit for magnet MU at contact hl and the selector wipers are drivento their home 1 position in which they are stopped by the deenergizationof magnet MU on the opening of Closure of contact h8 completes a homingcircuit for the digit switch over contacts al, DONZ, clm and b6 and thedigit switch is restored to normal. With the digit switch and theselecting switch both at normal battery is again connected overresistance YA to wire p to enable the selector to be taken into use foran- 1 other call. with relay H.

Relay WS, if operated, is released What I claim as new and desiretosecure by 1 Letters Patent is:

1. In an automatic telephone system, a single the operation of saidselector, a transfer relay operated during the said train ofimpulses'and;

freleased after the completion thereof means, in-

a searching movementfollowing such release to select. any desired one ofsaid outletv groups and an idle outlet therein, means independent ofsaid marker for starting said selector at times in a preliminarymovement prior to such release, and means for controlling the extent ofeach of said movements dependent on the condition of 'one of saidmarking positions in response to a train of impulses to cause saidselector to hunt an idle outlet in either of said groups of outletsdepending on its starting position, a transfer relay, means foroperating said relay during the said preliminary operation and releasingit prior to the said outlet hunting operation, a stopping circuitprepared by said relay in its operated condition for stopping thepreliminary operation of said selector when said second startingposition is reached, and a second stopping circuit prepared by saidrelay in its released condition for stopping the outlet huntingoperation of said selector when an idle outlet is reached in theselected group of outlets.

3. In an automatic telephone system, a single motion selector, first andsecond main groups of outlets accessible to said selector, sub-groups ineach of said main groups, first and second starting positions for saidselector, means responsive to a single train of dial impulses forcausing said selector to select a desired sub-group of outlets in eitherof said main groups depending on the starting position of said selector,said selector then acting automatically to select an idle outlet in saidselected sub-group, a pair of line conductors incoming to said selector,a selector line relay connected to one of said conductors, a selectorstarting-position relay connected to the other of said conductors, meansfor operating both of said relays in series over said line conductorsupon seizure of the selector whenever it is desired to select an outletin said second group of outlets, and means operated in response to suchoperation of said starting-position and line relays for driving saidselector to said second starting position.

4. In a rotary type selector for use in an automatic telephone system, aset of contact banks and wipers, first and second main groups of outletsconnected to said contact banks, sub-groups in each of said main groups,first and second starting positions for said wipers. a marker operatedresponsive to a single dialled digit for causing said selector to selectany of said subgroups and an idle outlet therein in either of said maingroups of outlets depending on the starting position of said wipers, asecond set of contact banks and wipers, other outlet groups similarlyconnected to said second set of contact banks, a wiper switching relay,contacts on said relay for selecting either of said wiper sets, saidrelay being operated momentarily upon seizure of the selector in casethe wanted group is in a second main group of outlets, means operated inresponse to such preliminary operation of said .relayto cause the wipersto advance to their sec-- ond starting position, and means for operatingand holding said relay in response to the dialled group selecting digitto select said second set of wipers in case the wanted outlet group isconnected to said second set of contact banks.

5. In a telephone system, a rotary type selector, contact banks forsaidselector, a first and a second main group of outlets, sub-groups ineach of said main groups, a marker, said marker being set in response toa dialled digit to mark a sub-group in each of said main groups forselection, a transfer relay operated during the setting of said markerand released after such setting to cause said selector to select one ofsaid marked subgroups and an idle outlet therein, a marking bank forsaid switch for marking said subgroups for selection in accordance withthe setting of said marker, a first and a second starting position forsaid selector, a first and a second start contact for said marking bank,a permanent marking for said second start contact in said marking bank,means for causing said selector to advance in a preliminary movementupon seizure in case it is desired to select a sub-group in said secondgroup of outlets, means for operating said transfer relay also duringsaid preliminary movement, and a stopping circuit including saidpermanently marked second start contact and front contacts on saidoperated transfer relay for arresting said preliminary movement andstopping said selector in its second starting position.

6. In an automatic telephone system, a rotary type selector switch,contact banks and wipers for said switch, two main groups of outletsconnected to said banks, sub-groups of outlets in each of said maingroups, first and second starting positions for said wipers, a pair ofspeech conductors incoming to said switch, a pulsing relay normallyconnected to one of said conductors. a discriminating relay normallyconnected to the other of said conductors, means for momentarilyoperating said discriminating relay in series with said pulsingrelayupon seizure of said selector to advance said wipers away from theirfirst starting position in case it is desired to select'a sub-group ofoutlets in said second main group, off-normal contacts on said switchfor maintaining said advance independently of said discriminating relay,a stopping relay for said switch, back contacts on said stopping relayin series with said off-normal contacts, means for operating saidstopping relay and opening said back contacts to stop said advance andsaid wipers in said second starting position, and impulse responsivemeans operated under the control of said pulsing relay in response to asingle dialled digit for causing said wipers to select a particulargroup of outlets in either of said main groups depending on the startingposition of said wipers.

7. In a telephone system, a single motion selector switch, wipers forsaid switch, two main groups of outlets accessible to said Wipers, anormal and a second starting position for said Wipers, means for causingsaid wipers to select an idle outlet in either of said main groups ofoutlets depending on the starting position of said wipers, a pair ofconductors incoming to said switch, a relay normally connected to one ofsaid conductors, means for momentarily operating said relay upon seizureof said switch whenever the second group of outlets is wanted, a startcircuit completed responsive to said relay operation for advancing saidwipers away from their normal starting position, oif-normal contactsoperated when said wipers leave said normal starting position forcontinuing said advance independently of said start circuit, means forstop- D said Wipers automatically at said second starting position, andfront and back contacts reversed by said switch in each of said normaland second starting positions to cause different operations upon thecompletionof the selection of an idle outlet, depending on which of saidmain groups of outlets is involved in said selection.

8. In an automatic telephone system, a rotary type selector, a first anda second set of wipers for said selector, a first and a second maingroup of outlets respectively accessible to each of said sets of wipers,sub-groups in each of said main groups, a normal and a second startingposition for said wipers, a marker switch for said selector operated'bydial pulses, means for causing the wipers of said selector to select anidle outlet in one of said sub-groups in either of said main groupsdepending on the starting position of said wipers and the operatedposition of said marker switch, a wiper switching relay, means forcausing a preliminary operation of said relay upon seizure of saidselector, means operated responsive to the said preliminary operation toadvance said selector from its normal to its second starting position, apair of wiper-switching contact banks for said. marker switch, midnormalcontacts reversed by said selector in its second starting position,means for again operating said wiper switching relay through either ofsaid wiper-switching contact banks depending on the position of saidmidnormal contacts in case it is desired to select an outlet accessibleonly to said second set of selector wipers, and contacts operated bysaid wiper switching relay to cause such selection to occur through saidsecond set of selector wipers.

9. In an automatic telephone system, a rotary type selector, speechconductors incoming to said selector, a first and a second rank of bankcontacts for said selector and a first and a" second main group ofoutlets connected respectively thereto, sub-groups in each of said maingroups, a normal and a second startin position for said selector; amarker switch operated responsive to a dialled digit to cause saidselector to select an idle outlet in either of said main groups and,

depending on the digit dialled, in any one of the sub-groups therein;discriminating means operated upon seizure of said selector for causingsaid selector to advance from its normal starting position to its secondstarting position preliminary to its outlet selecting operation in casethe desired outlet is in said second main group of outlets, a transferrelay operated during the dial pulses and released at their conclusionto initiate theoutlet selecting operation, a switching relay operatedupon the selection of an idle outlet to extend said speech conductors tosuch selected outlet, means for advancing said selector to the lastcontact of the rank of contacts over which it is searching in case noidle outlet is available in the selected sub-group, and means foroperating said switching relay and re-operating said transfer relay whenthe said last contact is DOUGLAS PERCY LONG.

